Meal-dependent fluctuations of blood glucose and corresponding endocrine signals such as insulin are thought to provide important regulatory input for central nervous processing of hunger and satiety. Since food intake also triggers the release of numerous gastrointestinal signals, the specific contribution of changes in blood glucose to appetite regulation in humans has remained unclear. Here we tested the hypothesis that inducing glycemic fluctuations by intravenous glucose infusion is associated with concurrent changes in hunger, appetite, and satiety...

BACKGROUND: The dorsolateral prefrontal cortex (DLPFC) plays an important role in appetite and food intake regulation. OBJECTIVE: Because previous data revealed that transcranial direct current stimulation (tDCS) of the DLPFC reduces food cravings, we hypothesized that repetitive electric stimulation of the right DLPFC would lower food intake behavior in humans. DESIGN: In a single-blind, code-based, placebo-controlled, counterbalanced, randomized crossover experiment, 14 healthy young men with body mass index (in kg/m(2)) from 20 to 25 were examined during 8 d of daily tDCS or a sham stimulation...

Hyperglycemia is a common phenomenon in the early phase of brain injury (BI). The management of blood glucose levels after BI, however, is subject of a growing debate. The occurrence of elevated blood glucose concentrations is linked to increased mortality and worse neurologic outcomes indicating the necessity for therapeutic glucose-lowering. Intensive glucose-lowering therapy, on the other hand, inevitably results in an increased rate of hypoglycemic episodes with detrimental effects on the injured brain...

Obesity is a global epidemic associated with a series of secondary complications and comorbid diseases such as diabetes mellitus, cardiovascular disease, sleep-breathing disorders, and certain forms of cancer. On the surface, it seems that obesity is simply the phenotypic manifestation of deliberately flawed food intake behavior with the consequence of dysbalanced energy uptake and expenditure and can easily be reversed by caloric restriction and exercise. Notwithstanding this assumption, the disappointing outcomes of long-term clinical studies based on this assumption show that the problem is much more complex...

Shortened nocturnal sleep impairs morning glucose tolerance. The underlying mechanism of this effect is supposed to involve a reduced fraction of slow wave sleep (SWS). However, it remains unanswered if impaired glucose tolerance occurs due to specific SWS reduction or a general disturbance of sleep. Sixteen healthy men participated in three experimental conditions in a crossover design: SWS suppression, rapid eye movement (REM)-sleep disturbance, and regular sleep. Selective sleep stage disturbance was performed by means of an acoustic tone (532Hz) with gradually rising sound intensity...

Sleep and endocrine function are known to be closely related, but studies on the effect of moderate sleep loss on endocrine axes are still sparse. We examined the influence of partial sleep restriction for 2 days on the secretory activity of the thyrotropic axis. Fifteen healthy, normal-weight men were tested in a balanced, cross-over study. Serum concentrations of thyrotrophin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) were monitored at 1-h intervals during a 15-h daytime period (08:00-23:00 h) following two nights of restricted sleep (bedtime 02:45-07:00 h) and two nights of regular sleep (bedtime 22:45-07:00 h), respectively...

Sleep enhances memory consolidation. Bearing in mind that food intake produces many metabolic signals that can influence memory processing in humans (e.g., insulin), the present study addressed the question as to whether the enhancing effect of sleep on memory consolidation is affected by the amount of energy consumed during the preceding daytime. Compared to sleep, nocturnal wakefulness has been shown to impair memory consolidation in humans. Thus, a second question was to examine whether the impaired memory consolidation associated with sleep deprivation (SD) could be compensated by increased daytime energy consumption...

BACKGROUND: Sleep loss has been shown to reduce secretory activity of the pituitary-gonadal axis in men, but the determinants of this effect are unknown. OBJECTIVE: To discriminate the effects of sleep duration and sleep timing on serum concentrations of luteinizing hormone (LH), testosterone (T) and prolactin (PRL). METHODS: Fifteen young, healthy men (27·1 ± 1·3 years; BMI, 22·9 ± 0·3 kg/m(2) ) were examined in a condition of sleep time restriction to 4 h (bedtime, 02:45 -07:00 h) for two consecutive nights and in a control condition of 8 h regular sleep (bedtime, 22:45-07:00 h)...

AIMS: Plasma glucose levels influence growth hormone concentrations. Oral contraceptives are known to affect circulating growth hormone levels and glucose metabolism. While growth hormone plays an important role in hypoglycaemia counter-regulation, it has been shown that oral contraceptives increase growth hormone concentrations. In this context, we tested if serum growth hormone concentrations display a differential response on glycaemic variations in healthy women using oral contraceptives and those not using contraceptives...

BACKGROUND: Controlled transcranial stimulation of the brain is part of clinical treatment strategies in neuropsychiatric diseases such as depression, stroke, or Parkinson's disease. Manipulating brain activity by transcranial stimulation, however, inevitably influences other control centers of various neuronal and neurohormonal feedback loops and therefore may concomitantly affect systemic metabolic regulation. Because hypothalamic adenosine triphosphate-sensitive potassium channels, which function as local energy sensors, are centrally involved in the regulation of glucose homeostasis, we tested whether transcranial direct current stimulation (tDCS) causes an excitation-induced transient neuronal energy depletion and thus influences systemic glucose homeostasis and related neuroendocrine mediators...

The anticipation of food intake comprises endocrine changes that according to animal experiments include a rise in HPA axis activity. In humans, HPA axis responses to food anticipation and withdrawal, although of clinical relevance, have not been thoroughly examined. We assessed neuroendocrine and psychological effects of food anticipation and of withholding anticipated food in healthy human subjects. Food anticipation was induced in 14 men at 0800 h by the announcement and subsequent presentation of a breakfast buffet...

STUDY OBJECTIVES: Epidemiological studies point to a strong association between short sleep duration and the development of diabetes. We examined the hypothesis that short-term sleep loss decreases glucose tolerance and insulin sensitivity and, if so, how these changes relate to hypothalamic-pituitary-adrenal (HPA) secretory activity and markers of subclinical inflammation. DESIGN: In a balanced, within-subject design, circulating glucose, insulin, C-peptide, glucagon, ACTH, cortisol, and IL-6 levels were closely monitored during a 15-h daytime period following 2 nights of restricted sleep (02:45-07:00) and 2 nights of regular sleep (bedtime 22:45-07:00), respectively...

Undetected nocturnal hypoglycaemia frequently occurs in patients with diabetes, having a negative influence on well-being, counterregulation against and awareness of subsequent hypoglycaemia, and even causing sudden death in some cases most likely by inducing cardiac arrhythmia. Sleep markedly weakens the neuroendocrine defence mechanism against hypoglycaemia by shifting the glycaemic threshold for counterregulatory activation to lower levels. While hypoglycaemia triggers awakening in healthy subjects, patients with type 1 diabetes frequently fail to awake in the presence of low plasma glucose levels...

CONTEXT: The risk to develop dementia is significantly increased in diabetes mellitus. Memantine, an N-methyl-D-aspartate receptor antagonist, which is clinically applied in dementia, has been shown to exert neuroprotective effects under hypoglycemic conditions in rats. OBJECTIVE: We hypothesized that memantine may prevent hypoglycemia-induced decrements in the cerebral high-energy phosphate, i.e. ATP, metabolism to exert its neuroprotective action under these conditions...

AIM: Sleep disturbances induce proinflammatory immune responses, which might increase cardiovascular disease risk. So far the effects of acute sleep deprivation and chronic sleep illnesses on the immune system have been investigated. The particular impact of shift work induced chronic circadian disruption on specific immune responses has not been addressed so far. METHODS: Pittsburgh-Sleep-Quality-Index (PSQI) questionnaire and blood sampling was performed by 225 shift workers and 137 daytime workers...